feat(app): optional vertical tab rail

[BYK]

Issue for this PR

Closes#36942

Type of change

• New feature

What does this PR do?

Adds an opt-in vertical tab layout, toggled from Settings › General. Horizontal tabs stay the default and nothing is removed.

The rail is resizable (persisted width) and collapsible to an icon-only strip that reveals on hover. It reuses the existing @container query that already hides tab titles at narrow widths, so there's no separate render path. Home and new-tab buttons move into the rail but call the same titlebar commands/tab actions, so no logic is duplicated — the titlebar stays mounted and just hides its tab row in vertical mode (hideTabs prop). Two extra options: place the rail on the right (mirrored layout), and hide the session-header review button.

I also enriched the session-header title with project name, branch/worktree, and a working dot, since collapsed/narrow tabs lose that context.

How did you verify your code works?

Ran bun typecheck and a full app build + smoke test. Manually tested toggling vertical/horizontal, left/right rail, resize, collapse, hover-reveal, and the review-button toggle in the desktop build.

Screenshots / recordings

Checklist

• I have tested my changes locally
• I have not included unrelated changes in this PR

[github-actions]

Thanks for updating your PR! It now meets our contributing guidelines. 👍

[punyamsingh]

@Hona hey, can we take this faster?